blender python api custom GUI
Using panels in 2.8+
It's my opinion that many (including my previous self) get over enamoured with invoking modal dialog props dialogs.
Currently question code has some empty operator (execution wise) that is basically  a draw method. Often I see code where the functionality of the operator used to draw a popup could be replaced entirely by a group property and update methods on the individual properties, hence may as well put in panel code.
IMO if you want a nice stable UI use a panel
Since the advent of 2.8 there is  the ability to

absolutely size panel content

Popup a panel with an operator wm.popup_panel(...)

Popup a panel from draw method (no operator layout.popover(...)

Make child panels.


Here is an example which I've demonstrated in text editor.  (based from good old Hello World Panel template)
In the UI N panel (context.region == 'UI') the x ui width is set to 0 making the add cube operator button the width of the panel, if invoked from the FOOTER region then the panel is 20 wide.

import bpy


class HelloWorldPanel(bpy.types.Panel):
    &quot;&quot;&quot;Creates a Panel in the Object properties window&quot;&quot;&quot;
    bl_label = &quot;Hello World Panel&quot;
    bl_idname = &quot;TEXT_PT_hello&quot;
    bl_space_type = 'TEXT_EDITOR'
    bl_region_type = 'UI'


    def draw(self, context):
        print(context.region.type)
        layout = self.layout
        layout.ui_units_x = 0 if context.region.type == 'UI' else 20
        obj = context.object

        row = layout.row()
        
        row.label(text=&quot;Hello world!&quot;, icon='WORLD_DATA')

        row = layout.row()
        row.label(text=&quot;Active object is: &quot; + obj.name)
        row = layout.row()
        row.prop(obj, &quot;name&quot;)

        row = layout.row()
        row.operator(&quot;mesh.primitive_cube_add&quot;)

def draw_panel(self, context):
    op = self.layout.operator(&quot;wm.call_panel&quot;)
    op.name = &quot;TEXT_PT_hello&quot;
    self.layout.popover(&quot;TEXT_PT_hello&quot;)

def register():
    bpy.utils.register_class(HelloWorldPanel)


def unregister():
    bpy.utils.unregister_class(HelloWorldPanel)


if __name__ == &quot;__main__&quot;:
    bpy.types.TEXT_HT_footer.append(draw_panel)
    register()

Note: Given the desire is to have &quot;popup&quot; not close when mousing away, and be resizable consider opening a new window as discussed here
New window with Python API?